The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing charge enhancing additives, which impart or assist in imparting a negative charge to the toner resin particles and enable toners with rapid charging characteristics, and wherein there is selected as the toner pigment a magnetite, especially a spherical magnetite treated with a phosphate titanium coupling agent, and which magnetite is available from Toda Chemicals of Japan. In embodiments of the present invention, there are provided single component toners containing magnetites treated with or containing a coating of a phosphate titanium coupling agent. The toner compositions of the present invention in embodiments thereof possess rapid charging or admix characteristics, and maintain their triboelectric charging characteristics for an extended number of imaging cycles. Furthermore, the toner compositions of the present invention are substantially insensitive to relative humidity and enable developed images with excellent optical densities. The toners of the present invention possess improved relative humidity sensitivity as compared to related toners indicated herein. Moreover, the toners of the present invention enable developed images with excellent solid area densities (SAD) of, for example, from about 1.2 to about 1.5, and preferably from about 1.3 to about 1.5. Also, the toner compositions of the present invention can be selected for electrophotographic, especially xerographic imaging and printing processes.
Developer compositions with charge enhancing additives, which impart a positive or negative charge to the toner resin, are known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions. In this patent, there are disclosed quaternary ammonium compounds with four R substituents on the nitrogen atom, which substituents represent an aliphatic hydrocarbon group having 7 or less, and preferably about 3 to about 7 carbon atoms, including straight and branch chain aliphatic hydrocarbon atoms, and wherein X represents an anionic function including, according to this patent, a variety of conventional anionic moieties such as halides, phosphates, acetates, nitrates, benzoates, methyl sulfates, perchloride, tetrafluoroborate, benzene sulfonate, and the like; U.S. Pat. No. 4,221,856 which discloses electrophotographic toners containing resin compatible quaternary ammonium compounds in which at least two R radicals are hydrocarbons having from 8 to about 22 carbon atoms, and each other R is a hydrogen or hydrocarbon radical with from 1 to about 8 carbon atoms, and A is an anion, for example sulfate, sulfonate, nitrate, borate, chlorate, and the halogens such as iodide, chloride and bromide, reference the Abstract of the Disclosure and column 3; a similar teaching is presented in U.S. Pat. No. 4,312,933 which is a division of U.S. Pat. No. 4,291,111; and similar teachings are presented in U.S. Pat. No. 4,291,112 wherein A is an anion including, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens. There are also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica.
Also, there are disclosed in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there are disclosed in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other documents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; 4,394,430, and 4,560,635 which illustrates a toner with a distearyl dimethyl ammonium methyl sulfate charge additive.
Moreover, toner compositions with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. No. 4,404,271 a complex system for developing electrostatic images with a toner, which contains a metal complex represented by the formula in column 2, for example, and wherein ME (metal) can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include U.S. Pat. Nos. 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives. Further, TRH as a charge additive is illustrated in a number of patents such as U.S. Pat. No. 5,278,018, the disclosure of which is totally incorporated herein by reference.
In the aforementioned U.S. Pat. No. 5,278,018 there is illustrated a negatively charged toner with crosslinked resin particles, silane treated magnetite particles, wax particles, and a negative chromate charge additive. This patent discloses toner insensitivity to RH, see for example column 1, line 34. The SAD of the developed images of the '018 patent is inferior in some instances when compared to the SADs of the present invention as illustrated herein.
Toner compositions with surface additives of metal salts of fatty acids, colloidal silicas, and the like are known, reference some of the patents mentioned herein; U.S. Pat. Nos. 3,655,374; 3,720,617 and 3,900,588.
Illustrated in copending application U.S. Ser. No. 073,374 (now abandoned), the disclosure of which is totally incorporated herein by reference, is a single component toner composition comprising:
(i) toner particles, comprising: PA1 (ii) external additives comprising:
(A) from about 45 to about 90 parts by weight of a resin selected from copolymers or terpolymers comprising residues of (a) at least one vinyl monomer and (b) at least one ester of an alphamethylene aliphatic monocarboxylic acid; wherein the resin has a glass transition temperature ranging from about 45.degree. C. to about 55.degree. C. and a melt flow index ranging from about 25 to about 29 grams per 10 minutes at 150.degree. C. and a 2.16 kilogram load; PA2 (B) from about 2 to about 6 parts by weight of a charge enhancing additive; PA2 (C) an effective amount of a colorant; and PA2 (D) an effective amount of a low molecular weight wax; and PA2 (E) flow aid particles in an amount of from about 0.1 to about 0.6 part by weight per 100 parts of the weight of the toner particles; and PA2 (F) metal oxide particles in an amount of from about 1 to about 4 parts by weight per 100 parts of the weight of the toner particles; wherein components (i) and (ii) are blended for a time period and at a rate sufficient to cause the external additive particles to adhere to surfaces of the toner particles.